1. Field of the Invention
The invention relates to a light diffusion unit used for a portable electronic communication terminal, for instance.
2. Description of the Related Art
A portable electronic communication terminal such as a cellular phone is designed to include a light diffusion unit for introducing a light emitted from a light source such as a light-emitting diode (LED), to lens, a button or liquid crystal. A portable electronic communication terminal is recently required to be thinner and thinner, and lighter and lighter in weight. Accordingly, a light diffusion unit is also required to be as small as possible. To this end, for instance, an attempt has been made to form a light guide thinner for uniformly introducing a light emitted from a light source, to the light guide.
FIG. 1 is a cross-sectional view of a conventional light diffusion unit.
The illustrated light diffusion unit 101 is comprised of a substrate 105, a case 106 formed with a hole 106a and covering the substrate 105 therewith, a light source 104 mounted on the substrate 105, a light diffuser 103 arranged in the hole 106a of the case 106 for externally radiating a light emitted from the light source 104, and a light guide 102 arranged between the substrate 105 and the light diffuser 103 for introducing a light emitted from the light source 104, to the light diffuser 103.
In operation of the light diffusion unit 101, when the light diffuser 103 is downwardly pushed, the light guide 102 is deformed, resulting in that a projection formed on a lower surface of the light guide 102 pushes a switch 108 formed on the substrate 105. As a result of the switch 108 being pushed, the light source 104 is turned on, and hence, emits a light. The light source 104 emits a light not only when the switch 108 is pushed, but also when a call is transmitted or received, and a battery is being charged.
A light emitted from the light source 104 is introduced into the light guide 102, and is diffused in the light guide 102. Then, the thus diffused light illuminates the light diffuser 103 exposed out of the case 106.
In order for the substrate 105 not to be seen through the light diffuser 103, the substrate 105 and the switch 108 are covered with a sheet 107. The sheet 107 is composed of a material which reflects and/or diffuses a light, and assists a light to be diffused in the light guide 102.
However, if the light guide 102 does not have a sufficient thickness, a light emitted from the light source 104 is not adequately diffused in the light guide 102, resulting in that the light diffuser 103 cannot be uniformly illuminated. For instance, only an area of a surface of the light diffuser 103, closer to the light source 104, is only made bright, and, in contrast, an area of a surface of the light diffuser 103, remoter from the light source 104, is made dark. The light diffuser 103 would have greater uniformity in brightness such as mentioned above, if the light diffuser 103 had a greater surface area.
It would be quite difficult to solve the above-mentioned problem only by adding the sheet 107. It would be necessary to increase the number of a light source such as LED in order to introduce a greater amount of light to the light diffuser 103.
However, an increase in the number of a light source newly causes another problem of increased consumption of power.
Furthermore, if the light guide were designed to have a greater thickness, the light diffusion unit would be thicker, which is contradictory to the above-mentioned requirement that a portable electronic communication terminal is required to be thinner and lighter.
Japanese Unexamined Patent Publication No. 7-58815 has suggested an operating unit in a cellular phone, including a cabinet in which a main substrate is arranged and which is formed at an outer surface thereof with a recessed portion, a control substrate on which a plurality of contacts are formed by printing, and on which a light-emitting device is mounted, a sheet composed of light-permeable and elastic material, and having key tops defined by light-impermeably printing the sheet such that figures and letters remain not printed in areas in alignment with the contacts, and a cover formed with openings in alignment with the key tops, and formed with ribs for pushing the sheet.
Japanese Unexamined Patent Publication No. 2000-30561, which is based on French patent application No. 9803142, has suggested a contact detecting device including a first insulating film defining at least one dome having an inner surface on which a contact electrode layer is formed, and an outer surface, and a second insulating film supporting thereon a detecting circuit which detects whether the contact electrode layer is electrically connected thereto. A layer composed of electroluminescence material is formed directly on the first insulating film such that the layer is positioned on a flat surface surrounding the outer surface.
Japanese Unexamined Patent Publication No. 7-273854 has suggested a cellular phone including a key top plate composed of light-permeable synthetic resin. The key top plate is formed with upwardly projecting key tops. The key top plate is arranged at a rear of a case of the cellular phone such that key tops are exposed through holes formed with the case. A light-emitting diode is mounted on a lower surface of the key top plate. A light emitted from the light-emitting diode is introduced through the key top plate to the key tops for illuminating the key tops. A mirror-like reflection layer is formed either on a surface of the key top plate except the key tops, or on a rear surface of the case. As an alternative, the key top is covered at a surface thereof except the key tops with a mirror-like reflection sheet. A light having been introduced into the key top plate and having been reflected at the reflection layer or the reflection sheet is introduced into the key tops.
Japanese Unexamined Patent Publication No. 9-198902 has suggested a key illuminator in a cellular phone, including keys to be pushed by a user, formed at a lower surface thereof with a projection, and at least partially light-permeable between upper and lower surfaces, a case formed with windows in which the keys are arranged, a switch transmitting a control signal when pushed by the projection, and a planar light-emitter including a water-resistant illuminator which emits a light on receipt of power and which is in the form of a film, a transparent electrode adhered to a first surface of the planar light-emitter, and an electrode adhered to a second surface of the planar light-emitter. The water-resistant illuminator is formed with a hole through which the projection makes contact with the switch.
Japanese Unexamined Patent Publication No. 11-297161 has suggested a key structure used for a cellular phone, including a substrate, a base positioned above the substrate, a film formed on the base and having a plurality of pairs of fixed contacts, movable contacts covering the fixed contacts, key tops through which the movable contacts, and a light-emitting device which illuminates the key tops. The light-emitting device is positioned on the substrate, but below the base such that a light emitted from the light-emitting device passes through the base and the film.
The above-mentioned problem remain unsolved even in the above-mentioned Publications.
In view of the above-mentioned problems in the conventional light diffusion units, it is an object of the present invention to provide a light diffusion unit in which only a thickness of a light guide is increased without an increase in the number of a light source and further without an increase in a thickness of a portable electronic communication terminal including the light diffusion unit.
In one aspect of the present invention, there is provided a light diffusion unit including (a) a substrate formed with a first hole, (b) a case formed with a second hole and covering the substrate therewith, (c) a light source mounted on the substrate, (d) a light diffuser arranged in the second hole of the case for externally radiating a light emitted from the light source and (e) a light guide arranged between the substrate and the light diffuser for introducing a light emitted from the light source, to the light diffuser, the light guide partially making close contact with the light diffuser and being partially arranged in the first hole of the substrate.
For instance, the light guide may have a first extension extending outwardly therefrom above the substrate to cover the light source therewith.
The light guide may have a second extension extending outwardly therefrom above the substrate to cover therewith a switch mounted on the substrate such that when the light diffuser is downwardly pushed, the second extension pushes the switch, the switch being not in alignment with the light diffuser.
It is preferable that the first and second holes are in alignment with each other.
For instance, the light diffuser may be comprised of a body portion slidable through the second hole of the case, and a flange portion extending outwardly from the cylindrical portion at a bottom of the body portion and acting as a stopper when the body portion outwardly slides through the second hole.
The light guide may be marked with marks.
For instance, the light guide may be composed of resin or rubber.
It is preferable that the light guide is opaline in color.
There is further provided a light diffusion unit including (a) a substrate formed with a first hole, (b) a case having a first portion covering an upper surface of the substrate therewith and a second portion covering a lower surface of the substrate therewith, the first portion being formed with a second hole and the second portion being formed with a third hole, (e) a light source mounted on the substrate, (d) a first light diffuser arranged in the second hole of the first portion of the case for externally radiating a light emitted from the light source, (e) a second light diffuser arranged in the third hole of the second portion of the case for externally radiating a light emitted from the light source, and (f) a light guide arranged between the first and second light diffusers for introducing a light emitted from the light source, to the first and second light diffusers, the light guide having an upper surface at which the light guide makes close contact with the first light diffuser, a lower surface at which the light guide makes close contact with the second light diffuser, and a main body slidable through the first hole of the substrate.
The advantages obtained by the aforementioned present invention will be described hereinbelow.
In the present invention, the substrate is formed with a hole just below the light guide, which allows the light guide to have an increased thickness. This ensures an increase in a light-introduction and light-diffusion efficiency of a light emitted from the light source. As a result, the light diffuser can be uniformly illuminated.
In addition, even if the light diffuser had an increased area, since it is no longer necessary to increase the number of a light source, it would be possible to avoid an increase in power consumption.
Furthermore, the light diffusion unit in accordance with the present invention does not need to include a sheet such as a light-reflection sheet, ensuring a reduction in the number of parts constituting the light diffusion unit, and reduction in costs for fabricating the light diffusion unit.
As is obvious in view of the above, the present invention meets with the requirement for a thinner and lighter light diffusion unit, and is suitable to a cellular phone as a switch.
The second extension ensures that a switch is certainly pushed, even if the switch is located far away from the light guide.
The light diffusion unit which includes the first and second light diffusers at opposite sides of the light guide makes it possible to make illumination at opposite sides of the light diffusion unit without an increase in the number of a light source such as LED.
The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings.